Quinaldine or 2-methylquinoline is a simple derivative of a heterocyclic compound quinoline. Quinaldines are known to have varied applications which include anti-malarial drugs, dyes, food colorants, pH indicators, pharmaceuticals and pigments.
Pigments are known to have wide applications in human life such as coatings, paints, papers, adhesives, latexes, toners, textiles, fibers, plastics, cosmetics and inks. A large numbers of organic and inorganic yellow pigments are available. They differ by their brightness of shade, opacity, fastness requirements, physiological properties, and economic considerations. These properties influence the choice of the pigments depending on the end application. As well as being used in yellow paints, yellow pigments are also used in oranges, greens and browns. Quinophthalone pigment is an organic yellow pigment used as a chrome replacement in high quality finishes.
Quinophthalone pigment is prepared from quinaldine compounds. Shikizai Kyokaishi, 44 (1971), 316-324 discloses preparation of quinophthalone pigments using bis quinaldines.
German Patent No. 429176 discloses a process of preparing mono quinophthalones by reacting 3-hydroxy quinaldine with anhydride/imide of dicarboxylic acid followed by either halogenation or sulphonation reaction at 3-hydroxy position.
U.S. Pat. No. 5,106,980 discloses a process of preparing mono quinophthalones by condensing 8-aminoquinaldine with an optionally substituted phthalic anhydride in presence of molten benzoic acid as diluent at a temperature ranging between 123° C. to 200° C.
A method for preparation of bis quinophthalones having hydrogen or chlorine or methyl substituent at 8-position is disclosed in an article titled “Study on Quinophthalone Pigments” Shikizai Kyokaishi, 44 (1971), 316-324.The method disclosed in the article comprises two steps: i) fusing phthalic anhydride; and ii) adding 6, 6′-bis quinaldine and heating at 170° C. to 180° C. for 6 hours to 12 hours.
Quinaldine is generally prepared from aniline and paraldehyde via Skraup synthesis or from aniline and crotonaldehyde via Doebner-von Miller variation of the Skraup reaction or extracted from coal tar.
CN 1763013 discloses Preparation of 8-amino-quinaldine from 8-nitro-2-methyl-quinoline by hydrogenation in benzene solvent in the presence of Pd/C catalyst.
Shikizai Kyokaishi, 44 (1971), 316-324 “Study on Quinophthalone Pigments”, discloses a method of preparation of 8,8′-dimethyl-6,6′-bis-quinaldine and 8,8′-dichloro-6,6′-bis quinaldine. According to the disclosure, benzidine is reacted with crotonaldehyde in presence of concentrated sulfuric acid, nitrobenzene-m-sulfonic acid sodium and ammonium vanadate at about 110° C. for a period of about 6 hours. However, the yield of bis-quinaldines is on a lower side in the range of 25% to 66%. Shikizai Kyokaishi, 44 (1971), 316-324 also discloses preparation of bis-quinophthalone pigments using bis quinaldines.
British Patent 395063 discloses a process for preparing quinaldines, which consists of heating amine and crotonaldehyde in presence of ammonium vanadate and oxidizing agent such as nitrobenzene sulfonic acid. Nitrobenzene sulfonic acid is in-situ generated from nitrobenzene and sulfuric acid.
Another, British Patent 895090 discloses a process for preparing anti-bacterial product containing N4,N4-alkylene-N1,N1-alkylene-bis-4-amino-quinaldinium dihalides, which comprises reacting 4-halo quinaldine or 4-halo quinaldiniuim halide with α,ω-diaminoalkane and reacting the resulting N4,N4-bis-quinaldinium compound with α,ω-dihaloalkane.
Still another British Patent 980394 discloses the quinaldinium derivative and its method of preparation.
However, Bis-quinophthalones disclosed in Shikizai Kyokaishi, 44 (1971), 316-324, shows remarkable color fading when exposed for longer hours and are poor light resistant.
The mono-quinophthalone and bis-quinophthalone of the prior art typically, suffer from drawbacks such as poor light resistance, poor solvent resistance, poor hue and less stability.
Research on new quinophthalone compounds which obviates the drawback of the prior art is being carried out. Co-pending application 2991/MUM/2011 deals with new quinophthalone pigments.
Accordingly, there is felt a need to develop new quinaldine compounds for preparing quinophthalone compounds that obviates the drawback of the prior art as disclosed above.